<p>The effects of religiosity on organizational behavior have become a topic of interest in the fields of management and religion. However, whether religiosity is associated with green-related innovation has not been explored, and the underlying economic channels remain unclear. This study addresses this gap by conceptualizing both regional religiosity and industry peer effects as distinct dimensions of informal institutions that jointly shape corporate green innovation. Using Chinese listed companies in 2020 as research subjects and employing a spatial econometric model, this study systematically tests these relationships. A positive link between religiosity and green-related innovation in firms is observed, and a positive peer effect on green innovation is also identified. To reveal the economic channel, the mediating role of business performance is tested. The results clearly indicate that business performance mediates the link between religiosity and green innovation in firms: regional religiosity fosters a pro-social business environment that enhances business performance, which in turn provides the resources necessary for green innovation. Furthermore, this association is shown to be heterogeneous, with the effect being pronounced in non-state-owned enterprises but muted in state-owned enterprises, where managerial atheism may offset religious norms. Evidence is provided by this study that religion, as an informal institution, is conducive to firms’ green innovation, and the understanding of the role of informal institutions in shaping corporate environmental strategy in transitional economies is deepened.</p>